.header {
    height: 100px;
    line-height: 100px;
    text-align: center;
    background-color: skyblue;
    font-size: 30px;
    color: #020202;
    box-shadow: 0px 0px 10px #000;
}

/* 做调试时的简单适配 */
@media screen and (max-width: 768px) {
    .header {
        font-size: 20px;
    }
}
/* 做调试时的简单适配 */
@media screen and (max-width: 600px) {
    .header {
        font-size: 15px;
    }
}